The user has passed (or will pass) a markdown file of raw material. This is exploit: the exploring is done, the pile is fixed, commit to a path through it and mine the pile to fill each beat.

If the user did not say where to save the article, ask once and remember the path.

Then run a beat-by-beat journey, choose-your-own-adventure style:

Establish the prerequisites. Before any beats, settle with the user what the audience already knows walking in, the concepts that are grounded from the start. Everything else must be grounded by a beat before a later beat can use it. See Grounding.
Write 2–3 candidate starting beats, drawn from the raw material. Each is a different entry point into the article. Each may only lean on grounded concepts; note what new concepts each one grounds. Show the user the beats before writing to the article file. The user picks one. Preview what beats that pick unlocks, as if the user is seeing a little way down the path.
Once the user picks a starting beat, write only that beat to the article file. A beat may be one sentence or several paragraphs, whatever that beat naturally is. Stop there.
Re-read the article file from disk. Then offer 2–3 candidate next beats: different directions the journey could pivot to from where the article now stands. Each must be reachable from the current grounded set; note what each one grounds.
Loop steps 3–5 until the article reaches a natural end.

writing-beats

Grounding